Brake shoe assembly

ABSTRACT

A brake shoe assembly comprises a carrier plate and a brake shoe spring having between its ends a loop-shaped portion. The loop-shaped portion is supported in a recess in the carrier plate which opens onto a peripheral surface of the carrier plate via an opening. The largest width of the recess is greater than the smallest width of the opening. A fastening arrangement retains the loop-shaped portion of the spring in the recess against slipping out of the latter in the axial direction normal to the carrier plate. The fastening arrangement may include a projection in the recess which engages in a slot of the spring, a groove in the recess which partially receives the loop-shaped portion of the spring, or a pair of lugs at the axial ends of the loop-shaped portion of the spring which confine the carrier plate between themselves.

BACKGROUND OF THE INVENTION

The present invention relates to a brake shoe assembly.

There is already known a brake shoe assembly comprising a carrier plate,to which friction material is secured, and a brake shoe spring havingbetween its ends an arcuate or loop-shaped portion which is supported ina recess in the brake shoe, this recess being open towards the edge ofthe brake shoe, with the largest width of the recess being greater thanthe smallest width of the opening. A conventional brake shoe assembly ofthis type is known from the German printed and published patentapplication No. 29 37 149. In this construction, the brake shoe springis held in the recess of the carrier plate radially and simultaneouslyin a circumferential direction of the brake shoe due to the engagementof the spring at least with the surface bounding the recess. The brakeshoe holding spring is retained in position in axial direction of therecess, that is, normal to the peripheral opening of the recess, onlydue to the frictional contact between the brake shoe holding spring andcarrier plate. This frictional contact is attributable to the clampingengagement between the loop-shaped portion of the brake shoe spring andthe surface bounding the recess. If, for instance, the amount offriction between the ends of the brake shoe spring, which bear against abrake housing part, and the brake housing part is higher than the amountof friction between the loop-shaped portion and the recess, the brakeshoe spring is not able to follow the movement of the brake shoe in theevent of an axial displacement of the brake shoe, such as that resultingfrom the wear of the friction material. When this occurs, the brake shoespring slips out of the recess and can no more fulfill its function.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to avoid thedisadvantages of the prior art.

More particularly, it is an object of the present invention to provide abrake shoe assembly of the type hereunder consideration which does notpossess the disadvantages of the conventional assemblies of this type.

Still another object of the present invention is to so construct thebrake shoe assembly of the above type as to safely retain the spring inthe recess against movement out of the recess in direction normal to theplane of the carrier plate.

It is yet another object of the present invention to so design theassembly as not to interfere with the introduction of the arcuateportion of the spring into the recess in the radial direction of thelatter.

A concomitant object of the invention is to so construct the assembly ofthe above type as to be simple in construction, easy and inexpensive tomanufacture, easy to use, and reliable in operation nevertheless.

In pursuance of these objects and others which will become apparenthereafter, one feature of the present invention resides in a brake shoeassembly comprising a brake shoe including a carrier member that extendsalong a plane, and having a peripheral surface and a recess that opensonto a region of the peripheral surface and extends along an axistransverse to said plane, the recess having a narrower width, asconsidered in the aforementioned plane, closer to the aforementionedregion than more remotely therefrom; a spring member having two endportions and an arcuate portion between the end portions, the arcuateportion being substantially conformingly received in, and the endportions being situated outwardly of, the recess in an assembledposition of the spring member relative to the brake shoe; and fasteningmeans on at least one, and positively engaging in the assembled positionthe other, of the spring and carrier members for retaining the springmember on the brake shoe against relative movement at least in one axialdirection of the recess. This affords, in addition to the radialsecuring in position of the brake shoe spring, an axial retention inposition which prevents the spring from slipping out of the recess. Itwill be furthermore advantageous that the positive engagement providedby the fastening means also inhibits a swinging movement of the brakeshoe in relation to its support at the brake shoe spring. A rotationallysecured coupling of the brake shoe spring to the brake shoe will beachieved thereby, so that rattling noises cannot occur when driving.

In an advantageous construction according to this invention, the brakeshoe spring is designed as a leaf spring, and a projection is shaped atthe recess of the carrier plate projecting into a slot of the leafspring. The brake shoe spring is a punched part made of sheet metal, andits slot is punched out simultaneously with the punching process.Additional manufacturing costs with respect to the brake shoe spring arethereby avoided. The shaping of the projection may be achieved, forexample, after the punching process of the carrier plate in that ascraping tool is pressed into the wall of the opening of the recess andin that, in doing so, the material which rolls back chip-like in frontof this tool is urged against a counter-holding tool, as a result ofwhich the desired shape of the projection will be obtained.

It will be expedient for the projection completely to fill the slot. Itwill be obtained by the projection abutting on the surfaces of the slotthat both the displacement of the brake shoe axially of the recess andthe aforementioned swing movement of the brake shoe will be inhibited.

Suitably, the projection extends over the peripheral length of therecess. To achieve this, the recess will be first punched to a smallersize as compared to the finished size during the punching-out of thecarrier plate, and, subsequently, the material which has been scrapedoff the edge of the recess by means of a scraping tool used forfinishing to final size and which rolls back chip-like in front of thistool will be pushed in this recess in front of the tool to form theprojection or ridge. The projection may then be pressed to assume itsfinal shape by two shaping tools moving towards each other. If it isdesired to form the projection at the edge of the carrier plate, onlyone scraping tool will be required, while two scraping tools that movetowards each other will be required if it is desired to form theprojection in the central region of the recess. These scraping tools mayalso be able simultaneously to carry out the compression shapingprocess.

It is a frequent demand when using brake shoe springs that they shallnot project beyond the edges of the recess. This demand is met in theinventive brake shoe assembly, for example, in that the width of theleaf spring is not greater than the thickness of the carrier plate. Inthis arrangement, the projection is placed in the middle of the openingof the recess and projects into the slot of the brake shoe springlocated in the middle of the loop-shaped portion. This brake shoeassembly affords a fastening of the brake-shoe spring to the carrierplate which rigidly and reliably couples both parts to one another andnevertheless enables a quick mounting or dismounting which will beattained by simply compressing the loop-shaped portion and bysubsequently fitting it radially to or removing it radially from thecarrier plate.

In another advantageous constuction of the present invention, a grooveis formed in the recess. Then, the brake shoe spring extends into thegroove. When employing a wire spring, the groove is of a part-circularcross section. When employing a leaf spring, the groove is ofrectangular cross-section. It will be expedient to shape one projectionas a collar, while the opposite projection may be formed by at least oneweb which engages in a slot of the brake shoe spring opening towards theweb. The annular collar or rib can be manufactured, for instance, bymeans of a scraping tool, as has been described already above. After thefitting of the brake-shoe spring, the projections arranged on theopposite edge of the recess will be upset, by means of an embossingstamp, into the slots of the brake shoe spring provided for thispurpose. There is a positive engagement between the brake-shoe springand the carrier plate in this arrangement, and it will be no longerpossible to radially remove the brake shoe spring after the upsettingoperation. If only one projection engages the slot of the brake shoespring provided for this purpose, and if this projection is positionedat the carrier plate in the assembling direction of the brake-shoespring, repeated mounting and dismounting of the brake shoe spring willremain possible.

According to another advantageous concept of this invention, sheet-metallugs are arranged at the end surfaces of the loop-shaped portion of thebrake shoe spring. These lugs confine the carrier plate betweenthemselves at the area of the recess. The sheet-metal lugs are shaped atthe brake-shoe spring while it is being punched. No additionalmanufacturing costs will be incurred thereby. After the brake shoespring has been fitted to the carrier plate, the sheet-metal lugs willbe folded and urged against the carrier plate. It is, however, alsopossible to fold the sheet-metal lugs already prior to the mounting ofthe brake shoe spring so that, after the assembly, the resilientsheet-metal lugs will abut the carrier plate in positive and frictionalengagement therewith.

Advantageously, there is embossed an indentation at the end surface ofthe carrier plate close to the piston in the area of the recess, whichindentation stands out as an elevation from the opposite end surfaces ofthe carrier plate. It will be achieved by virtue of this embossing thatthe brake shoe spring does not project beyond the end surface of thecarrier plate close to the piston in the area of the loop-shapedportion.

BRIEF DESCRIPTION OF THE DRAWING

Above-mentioned and other features and objects of this invention willbecome more apparent by reference to the following description taken inconjunction with the accompanying drawing, in which:

FIG. 1 is a perspective partial view of the assembly of the invention inthe area where the brake shoe spring is fastened to the carrier plate;

FIG. 2 is a view similar to FIG. 1 but showing a modification;

FIG. 3 is a partial cross-sectional view through the area where thebrake shoe spring is fastened to the carrier plate according to FIG. 2;

FIG. 4 is a top plan view of still another modified construction of theinvention at the area where the brake shoe spring is fastened to thecarrier plate;

FIG. 5 is a partial cross-sectional view taken through the modifiedconstruction according to FIG. 4;

FIG. 6 is a perspective view of the brake shoe assembly of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawing in detail, it may be seen that it showsseveral modifications of the brake shoe assembly according to theinvention. Therefore, the same reference numerals have been assigned tothe corresponding parts. Each assembly comprises a carrier plate 1 and abrake shoe spring 2. Friction material or lining, shown as a frictionpad in FIG. 6, is secured to an end surface 3 of the carrier plate 1. Anarcuate or a loop-shaped portion 6 is formed between the ends 4, 5 ofthe brake shoe spring 2. The loop-shaped portion 6 is supported in arecess 8 provided in the carrier plate 1. The recess 8 is open towardsan edge or peripheral portion 7 of the carrier plate 1. The largestwidth W1 of the recess 8 is greater than the smallest width W2 of anopening 9 that opens onto the peripheral portion 7. The recess 8 is asubstantially cylindrical bore in which the loop-shaped portion 6 issupported. Arranged at the carrier plate 1 and/or at the brake-shoespring 2 are fastening means 10 which provide for a positive engagementnormal to the opening 9 of the recess 8, that is, axially of the recess8. The brake shoe spring 2 is designed as a leaf spring.

In FIG. 1 of the drawing, the fastening means 10 is constituted by aprojection formed as a partially annular collar or ridge 11 whichpenetrates into a slot 12 of rectangular cross section provided in theleaf spring 2. The annular collar 11 extends over the periphery of therecess 8, ends flush with the end surface 3 of the carrier plate 1 andextends over a part of the axial dimension of the open recess 8.Surfaces 13 forming the rectangular cross-section of the slot 12 bearagainst associated surfaces 14 of the annular collar 11 which lieopposite to them, as a result of which the annular collar 11 fills upthe slot 12. The loop-shaped portion 6 ends flush with an end surface 15of the carrier plate 1 lying opposite to the end surface 3. A front part16 of the loop-shaped portion 6 projects from the end surface 3 so thatthe width of the loop-shaped portion 6 in the longitudinal or axialdirection of the recess 8 is larger than the thickness of the carrierplate 3. At the transition from the loop-shaped portion 6 to the ends 4,5 of the brake shoe spring 2, the width of the brake shoe spring 2 isreduced to correspond to the thickness of the carrier plate 1.

In FIGS. 2 and 3 of the drawing, the width of the brake shoe spring 2 issmaller than the thickness of the carrier plate 1. The loop-shapedportion 6 is supported in the recess 8. The carrier plate 1 is providedwith a groove 22 within the recess 6. The loop-shaped portion 6 isaxially held in the axial direction of the open recess 8 by fasteningmeans 10 in the form of projections which extend on both sides of therecess 8 at the end surfaces 3, 15 of the carrier plate 1. In thisarrangement, the fastening means 10 again includes the annular collar orrib 11 having a shape corresponding to that of the annular collar 11according to FIG. 1 of the drawing. However, the annular collar 11 ofFIG. 3 is situated on the other side of the carrier plate 1 at the endsurface 15. The fastening means 10 further includes webs 23 which areshaped at the end surface 3 at the edge of the open recess 8 and whichare manufactured, for example, by upsetting. The webs 23 engage in slots12 of the brake shoe spring 2 which are open towards the webs 23. Thesurfaces 13 bounding the slot 12 bear against the surfaces 14 of thewebs 23 which lie opposite to them.

In FIGS. 4 and 5 of the drawing, the fastening means 10 includessheet-metal lugs 18 arranged at the surfaces 17 on both sides of theloop-shaped portion 6. The lugs 18 confine the carrier plate 1 betweenthemselves at the area of the recess 8. At the end surface 15 of thecarrier plate 1 in the area of the recess 8, there is embossed anindentation 19 which stands out as an elevation 20 from the opposite endsurface 3 of the carrier plate 1. The recess 8 is formed by a smoothcylinder bore 21. The lug 18 close to the end surface 15 of the carrierplate 1 is accommodated in the indentation 19.

While we have described above the principles of our invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of our invention as set forth in the accompanying claims.

We claim:
 1. A brake shoe assembly comprising:a brake shoe including acarrier member that extends along a plane, and having a peripheralsurface and a recess that opens onto a region of said peripheral surfaceand extends along an axis transverse to said plane, said recess having anarrower width, as considered in said plane, closer to said region thanmore remotely therefrom; a spring member having two end portions and anarcuate portion between said end portions, said arcuate portion beingsubstantially conformingly received in, and said end portions beingsituated outwardly of, said recess in an assembled position of saidspring member relative to said brake shoe; fastening means on at leastone, and positively engaging in said assembled position the other, ofsaid spring and carrier members for retaining said spring member on saidbrake shoe against relative movement at least in one axial direction ofsaid recess, wherein said spring member is a leaf spring having at leastone opening; and wherein said fastening means includes at least oneprojection on said carrier member received in said opening in saidassembled position, and wherein said opening is situated in said arcuateportion of said leaf spring; and wherein said projection is situatedwithin said recess.
 2. The brake shoe assembly as defined in claim 1,wherein said opening has a slot-shaped configuration; and wherein saidprojection has a ridge-shaped configuration substantially conforming tothat of said opening.
 3. The brake shoe assembly as defined in claim 2,wherein said slot-shaped opening and said ridge-shaped projection extendsubstantially circumferentially of said recess in said assembledposition.
 4. A brake shoe assembly comprising:a brake shoe including acarrier member that extends along a plane, and having a peripheralsurface and a recess that opens onto a region of said peripheral surfaceand extends along an axis transverse to said plane, said recess having anarrower width, as considered in said plane, closer to said region thanmore remotely therefrom; a spring member having two end portions and anarcuate portion between said end portions, said arcuate portion beingsubstantially conformingly received in, and said end portions beingsituated outwardly of, said recess in an assembled position of saidspring member relative to said brake shoe; fastening means on at leastone, and positively engaging in said assembled position the other, ofsaid spring and carrier members for retaining said spring member on saidbrake shoe against relative movement at least in one axial direction ofsaid recess and wherein said fastening means includes means for definingat least one wall member in said carrier member within said recess, saidwall member axially abutting at least a part of said arcuate portion ofsaid spring member.
 5. The brake shoe assembly as defined in claim 1,wherein said wall member includes at least one rib in said recessadjoining said part of said arcuate portion of said spring member at oneaxial end of the latter in said assembled position.
 6. The brake shoe asdefined in claim 5, wherein said fastening means further includes atleast one web portion on said carrier member situated at the other axialend of said spring member in said assembled position.
 7. The brake shoeassembly as defined in claim 6, wherein said spring member is a leafspring having an axial end portion at said other end and at least onerecessed zone in said axial end portion which at least partiallyreceives said web portion in said assembled position.